I tried the whole process several times. I hactivated.

I have an Iphone 3gs on 3.1.2 firmware with baseband 05.11.07. I did jailbreak and unlock using blackra1n and sn0w. When I use my T-mobile SIM, it initially comes with some bars and then gradually goes away and stays in NO Service. I get a message network lost. Your selected cellular network is no longer available. you can choose a different network in settings.
I have turned off 3G. I also tried setting Airplane Mode ON/OFF and reset network settings but no success. Please HELP!!!